1. Field of the Invention
This invention relates to spinal implants, and more specifically, the invention relates to an implant having at least one resilient, elastic or flexible arm adapted to have an arm axis that becomes generally parallel to an axis of a screw that is received in the implant.
2. Description of the Related Art
Many types of prosthetic devices have been proposed in the past. For example, U.S. Pat. No. 5,192,327 to Brantagan concerns a surgical prosthetic modular implant used singularly or stacked together to support and fuse together adjacent vertebrae or to totally or partially replace one or more vertebrae in a vertebral column. Other surgical implant devices and methods are shown in U.S. Pat. Nos. 5,192,327; 5,261,911; 5,713,899; 5,776,196; 6,136,002; 6,159,245; 6,224,602; 6,258,089; 6,261,586; 6,264,655; 6,306,136; 6,328,738; 6,592,586; 7,182,782 and 7,641,701. Some or all of these devices have improved the success rate and have simplified the surgical techniques in inter-body veritable fusion.
Among some of the problems associated with the prior art devices is that after the device is inserted into a patient during a surgical procedure, there was a possibility of retropulsion of the inter-body device and graft material into the spinal cord or other neurological element.
Another problem with the prior art devices is that grafting material, which was inserted into the devices during the surgical procedure, could not easily be inserted from an anterior direction.
Another problem with some prior art systems is that the screws or fasteners which secured implant to bone sometimes had a tendency to unscrew themselves because the implant itself may move or withdraw.
In some prior art implants, screws are placed at an angle relative to the plane in which the cage lies so that the screws can be screwed directly into an upper vertebra and/or a lower vertebra. While solutions for retaining screws in the implant plates have included, for example, the use of a resilient arm and approaches used in U.S. Pat. No. 7,641,701, these approaches do not work as effectively with implants that use angled screws. Such approaches are also not practical for use with implants that do not have available space for using an arm.
What is needed, therefore, is a screw retaining system that is particularly adapted for use with implants having angled screws. What is also needed is a system and means for locking a multi-component implant assembly together.